Research On Broadband Piezoelectric Vibration Energy Harvester With Clamped-clamped Beams

With the widespread application of wireless sensor and microelectronic devices,new requirements and challenges are put forward for energy supply technology.Due to high electromechanical conversion efficiency and energy density,piezoelectric vibration energy harvesting technology have attracted extensive attention from researchers.In order to improve the output,the main methods are to increase the size and design new structures.Therefore,researchers are gradually paying attention to the vibration characteristics and output performance of the piezoelectric vibration energy harvester with clamped-clamped beams.In this paper,two kind of energy harvesters with clamped-clamped beams are designed.According to the characteristics of composite beam,the natural frequency formulas are derived and the nonlinear behavior is explained.The results of finite element simulation show that the stress is symmetrically distributed on the beam and relative error between theoretical and simulation is 1.14%for the natural frequency.In addition,the devices are fabricated with MEMS technology and the performance of the energy harvester is tested.XRD analysis show that the PZT thin film is<110>crystal phase,and the perovskite structure is formed inside completely.The test results of dielectric performance show that the capacitance fluctuation of PZT thin film does not exceed 3.5 nF at voltage of 1 V and frequency between 50 to 10000 Hz.The dielectric loss also remains in the range of 0.0204 to 0.0488 and the dielectric constant varies from 1436 to 1686.The leakage current are lower than 4×10^-9A when the voltage sweeps from 0 to 37V with a step length of 0.01.The ferroelectric performance are tested with Sawyer tower circuit and when the reference capacitance increases,the remanent polarization and the coercive electric field get larger than that before.Besides,it has hysteresis loop saturation according to the result.In addition,two kind of structures are loaded with displacement and the resilience force is tested.The results suggest that the force of clamped-clamped beams are larger and faster than that of the cantilever beam,which also leads to the nonlinear behavior.Besides,the deformation of the trapezoidal beam is smaller than that of the rectangular beam which is good for the output of energy harvester.In terms of the output,a measuring system is set up to test the output of the energy harvester.The nonlinear behavior is verified according to the open loop output when the acceleration is 1m/s² and the bandwidths of the two kinds of the structure increase with the increase of the excitation intensity.When the vibration acceleration is 1g,the-3dB bandwidth of the clamped-clamped beams structure 1 and 2 is 105Hz and 118Hz,the maximum output voltages are 36.96mV and 45.46mV.It can be concluded that the trapezoidal beam is more advantageous than rectangular beam.The power test was performed on No.1 beam of Structure2.When the acceleration was 1g,the maximum output power is 112.63nW,and the optimal load is 23K?,in addition,the power density is about 554.55?W/cm³,which is greater than the same type of energy harvester.